1. Field of the Invention
The present invention relates to an optical transmission module or an optical module. In particular, the invention relates to an optical transmission module or an optical module having an optical connector mechanism.
2. Description of the Related Art
Optical communications systems for communications networks having a large capacity of data transmission have been developed for wide spread use and will continue to be further developed in the future considering the demand for multimedia in society.
Communications systems include optical transmission modules or optical modules that are placed in an optical network unit of an optical transmission network. However, since such optical transmission modules or optical modules are expensive, it is desirable to reduce their cost. One of the reasons why such modules are so expensive is that the conventional optical transmission modules or optical modules are pigtail type modules which cannot be readily detached from the optical fiber. Once the optical fiber is attached to the optical transmission module or optical module, it is difficult to perform reflow soldering and to handle the optical fiber itself.
Optical transmission modules or optical modules in which the optical fiber is capable of being detached have been proposed. For instance, a surface mountable optical module having a simple type optical connector structure to which an optical fiber is able to be attached is described in IEEE Transactions on Components, Packaging, and Manufacturing Technology-Part B, Vol. 19. No. 3, pp. 524-531, August 1996. This simple type of optical connector includes an optical connector pigtail for the optical fiber and a receptacle that receives the connector positioned at the edge of the optical module.
By using an optical module having an optical connector structure from which the optical fiber connector can be detached, it becomes relatively simple to perform reflow soldering and handling of the optical module, followed by connection of the optical fiber to the module. The cost of the optical module is also reduced by employing such type of optical connector structure.
However, in the conventional art, it is necessary to provide sufficient space along the surface of the mounting board adjacent to the receptacle at the edge of the optical module for connecting the optical fiber connector. The reason the space is provided is because the direction of movement of the connector with respect to the receptacle of the module is in parallel with the mounting board surface of the optical module. Since it is necessary to maintain such a space adjacent the module for the connector, other chip components cannot be mounted in the space. Therefore, in the conventional art, a problem arises in that it is difficult to mount several kinds of components on a board in order to achieve high density of the components or to mount the optical module on a central portion of the mounting board.
Accordingly, an object of the present invention is to solve the problem of the conventional art by providing an optical transmission module or optical module suitable for high density mounting.
Another object of the present invention is to provide an optical transmission module or optical module having an optical active component with a receptacle prepared at one edge of the optical module for receiving a plug to which an optical fiber is connected. The connection of the receptacle and the plug can be made in a detachable manner from above the module so that the plug is optically coupled with the optical module active component after mounting of the module on a mounting board or surface.
The optical components mounted in the optical module include an optical fiber, an optical waveguide, an optical device, etc. The housing of the module has a receptacle that is shaped to mechanically fit with the housing of the plug. Further, the plug includes a mechanism to move the optical fiber back and forth with respect to the plug.
In a circuit board having the optical transmission module or optical module of the invention mounted thereon, a plurality of electronic components can be placed peripherally around the optical transmission module or optical module, and it is still possible to detach the plug from the receptacle.
An optical connector relating to the present invention includes a receptacle having a first optical fiber extending to an edge of the optical module with a ferrule and a plug to which a second optical fiber is connected that is shaped to fit within with the receptacle in a detachable manner from above the receptacle. In particular, the plug is configured to hold the second optical fiber for optically connecting it with the first optical fiber. The plug preferably includes a mechanism for moving the second optical fiber with respect to the plug in the direction of lightwave propagation of the module. Such a mechanism may include a knob attached to a ferrule to which the second optical fiber is fixed and a resilient member (e.g., a spring) biasing the movement of the knob toward a position in which the ferrule of the plug engages a ferrule of the module.
Additionally, the present invention provides a method for connecting an optical connector for an optical fiber to a component. The method involves the use of a connector mounted to an optical fiber, such as a plug. The plug has a configuration or shape that interfits with the receptacle from above the module when the plug is pushed or placed in the receptacle. The optical fiber passes through the housing of the plug to the outside of the housing and is optically coupled to the tip of the first optical fiber installed in the receptacle after the plug and receptacle have been fit together. The method also provides for detaching the optical connector or plug from the receptacle by first withdrawing the ferrule of the plug from optical engagement with the ferrule of the receptable and then detaching the plug from the housing of the receptacle by removing it therefrom in an upper direction.
Through the aforementioned, a high density mounting of the optical transmission module or optical module can be realized.